The insulation of chambers of a wide variety of types and applications continue to present serious problems owing to the high temperatures involved and the severe operating conditions commonly present in such chambers. Traditionally and historically chambers of this type have been lined with various types of bricks, castables, or other dense refractories compounded to resist high temperatures. Such linings have many shortcomings and disadvantages well known to those skilled in this art including objectionably high weight, the need for high strength supporting structure, spalling, cracking and shattering, poor thermal shock properties, high cost of construction, maintenance and replacement, high heat storage, poor insulating ability, and others. In recent years lightweight non-rigid linings in a variety of types and construction and having certain superior properties have come into general usage. These linings are made of ceramic fiber material generally available in blanket form by depositing the fibers as formed on a moving conveyor as for example in accordance with the technique disclosed in the patent to Malone U.S. Pat. No. 3,615,964. The freshly formed fibers are deposited in layers along with a bonding agent to adhere the fibers together at points of cross-over. The resulting blanket has a thickness from a fraction of an inch up to 2', a density of 3-8 lbs. per cubic foot, and is readily flexed and wound into a roll of convenient handling size until ready for use. Some users subdivide these blankets into convenient handling size and attach one face directly to the furnace wall by ceramic cement mortar or the like. A lining of this thickness provides inadequate insulation unless applied over an existing lining and has an objectionably short service life and deteriorate prematurely under the harsh operating conditions normally prevailing in most high temperature chambers. Multiple layers of blanket can be attached to a furnace wall using appropriate mounting studs. Proper support has usually been a problem. Shrinkage also causes problems. Both result in tearing of the hot face blanket. Metallic studs are limited to 2250.degree. F. exposure and ceramic studs have thermal shock problems.
Various designers familiar with these problems have made a variety of proposals for improved modes of utilizing ceramic blanket material to provide a lining of any desired thickness with the fiber layers lying generally perpendicular to the supporting wall structure. Typical proposals of this character are disclosed in Sauder U.S. Pat. No. 3,706,870; Sauder U.S. Pat. No. 3,819,468; Balaz U.S. Pat. No. 3,832,815; Brady U.S. Pat. No. 3,854,262; Monaghan U.S. Pat. No. 3,892,396; Shelley U.S. Pat. No. 3,930,916; Sauder U.S. Pat. No. 3,940,244; Byrd U.S. Pat. No. 3,952,470; Greaves U.S. Pat. No. 3,990,203; Sauder U.S. Pat. No. 3,993,237; and Byrd U.S. Pat. No. 4,001,996. Each of these proposals embodies means for holding strips of flexible ceramic blanket material assembled with adjacent faces of the strips in side-by-side relation and secured to a supporting frame or backing mountable against a furnace or chamber wall. In most instances, this mounting backing is designed to compress the strips transversely of their thickness in an effort to increase its density and to compensate for shrinkage at higher temperatures. It is readily apparent that these techniques incur objectionable labor, assembly, and material costs and provide a lining having an inferior density and heat insulating characteristics.
It has also been proposed to form heat insulating components by a vacuum forming process in which a perforated evacuated mold is suspended in an aqueous solution or slurry comprising primarily inorganic ceramic fibers and suitable binder agents. These components are thoroughly mixed in a water suspension by suitable means such as hydropulper or other mixer. This composition is deposited on the perforated face of the mold connected to a vacuum pump. This process as practiced prior to this invention provides a mat of fibers having a maximum depth of about two inches. When that depth is reached the resistance to further filtering and removal of water and deposition of fibers becomes too high for further deposition of fibers.